They have spent the last year "scoping" an investigation; working out if they have the necessary powers and resources to look at what happened at Orgreave.

The IPCC has now taken a step, asking every force in England and Wales to check what information they hold in their archives relating to Orgreave.

But it's not enough for some.

The shadow Home Secretary says the IPCC should be replaced.

The organisation has been under huge pressure with fresh investigations also going on into the Hillsborough tragedy.

Extra powers, more investigators and new offices were needed to get that going.

The IPCC might need even more again to carry out a full investigation into what happened at Orgreave.

The request for additional information by the IPCC forms part of its "scoping exercise" into what went on in the police force, which is already under scrutiny over its role in the Hillsborough disaster.

It will then decide whether to carry out a full investigation.

The commission has been examining files in 65 boxes handed over by the South Yorkshire force. It is understood they contain specific information relating to events at Orgreave.

'Hugely complex'

There are more boxes, which are yet to be considered by the IPCC, that are thought to contain general information about the miners' strike, the watchdog said.

Ms Butts said what had already been received "can in no way be described as a complete record of events".

The watchdog's scoping exercise was "hugely complex", she added, and all police forces in England and Wales had been asked to search for any relevant documents.

The BBC Inside Out programme investigated the events following the arrest of more than 90 people at Orgreave, which saw some of the most shocking and infamous scenes of the bitter dispute.

Those charged with riot were later cleared after doubts were raised about police evidence.

'Raw emotions'

The BBC said it obtained copies of about 100 police witness statements, which programme makers said showed the extent to which officers used identical phrases to describe what they had seen.

"I appreciate it is now almost 30 years since the events at Orgreave and a year since South Yorkshire Police made a referral to us - and people will rightly want answers to the questions they have," Ms Butts said.

"I know how raw the emotions are in mining communities around Yorkshire and the rest of the country.

"I am committed to ensuring we conduct a thorough scoping exercise to ensure we have all the information at our disposal to make a definitive decision about what matters remain capable of investigation."

Ms Butts said the IPCC had also approached law firms which represented miners in relation to Orgreave to establish what documents they might hold.